This application claims the priority of German Patent Application No. 100 20 451.1 filed Apr. 26, 2000, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a selector device for a change-speed gearbox that has a selector shaft that can be subjected to an axial selecting force and is used for actuating gearwheel clutches and relative to which a choosing sleeve is arranged concentrically and in such a way that it can be displaced in a positively guided manner and fixed relative to a housing. It being possible to arrange the selector shaft in an axially displaceable manner in a significant angular position relative to the housing by a latching device but to fix it in an essentially rotationally fixed manner by a latching force that can be overcome.
Selector devices of this kind are distinguished especially by the fact that all that is required for the actuation of the selector shaft, both into its angular positions for initially choosing the new gear and into its axial end positions for engaging (selecting) the new gear, is to exert an external axial actuating force on the selector shaft and, consequently, only a single servomotor (linear motor) is required for automatic operation of the selector device.
In a known selector device of the type as in German Patent Document DE 196 10 104 C2, corresponding to U.S. Pat. No. 5,809,836, the choosing and selecting movements of the selector shaft are already kept small, and hence, short selection times are achieved by virtue of the fact that a gate with a corresponding sliding block is provided for the auxiliary mechanism. The gate has two gate portions, which are arranged offset relative to one another both in the directions of the axis of rotation of the selector shaft and by the differential angle of rotation enclosed between two adjacent significant angular positions of the selector shaft and run parallel to the axis of rotation. Of the mutually opposite ends of the gate portions, at least one end is associated with a gear position of the selector shaft. The gate furthermore has a central gate portion that runs at an angle to the axis of rotation of the selector shaft, this portion being associated with the neutral position of the selector shaft. In this known selector device, multiple shifts, i.e. shifts between two nonadjacent gears, are possible. If the old and the new gear involved in such a multiple shift are not in two adjacent significant angular positions of the selector shaft, the known selector device allows the use of a method for performing such a multiple shift, which requires long choosing and selecting paths. According to this method, the selector shaft passes through the neutral position alternately in both axial directions and the brake is held in the engaged state during its passage in one axial direction and in the disengaged state during its passage in the other axial direction. The direction of the axial motion of the selector shaft is reversed even before a gear position is reached, once a significant angular position that does not include the new gear position to be chosen has been reached and the neutral position has been departed from.
An object of the present invention is to further reduce the gear-change paths and times, especially for multiple shifts, in a selector device of the type stated at the outset.
According to the invention, this object is achieved by at least one additional choosing sleeve arranged concentrically and in such a way that it can be displaced in a positively guided manner relative to the selector shaft and can be fixed relative to the housing.
In the selector device according to the invention, at least one positively guided additional choosing sleeve appropriately coordinated with the positive guidance of the first choosing sleeve makes it possible to perform upshifts and downshifts that involve skipping one or more gears directly, i.e. without reversing the selector shaft several times.
Owing to the axial selecting force, it is possible in a particularly advantageous way to use low-cost linear motors, e.g. hydraulic pistons or electromagnets.
In the advantageous alternative embodiment of the selector device, at least one additional choosing sleeve and the respectively associated additional auxiliary mechanism make it possible, by appropriate coordination, in terms of their level and direction of action, of the transmission ratios of the auxiliary mechanism associated with the first choosing sleeve and of the respective auxiliary mechanism associated with the additional choosing sleeve, to perform upshifts and downshifts that involve skipping one or more gears directly, i.e. without reversing the selector shaft several times.
In an advantageous embodiment of the selector device, the equal but opposite transmission ratios of the auxiliary mechanisms ensure, inter alia, that when the selector shaft is actuated to disengage a mid-range gear and change to an adjacent significant angular position, only the first choosing sleeve has to be activated for an upshift and only the additional choosing sleeve has to be activated for a downshift.
In the case of a refinement of the selector device, which is advantageous particularly for multi-speed transmissions, direct downshifts, even those that involve skipping a number of gears, can be performed by activating an additional choosing sleeve.
Taking this as a starting point, an embodiment of the selector device according to the invention is advantageous also for a 5- or 6-speed transmission, for example, and in which it is possible to skip two or three gears in the case of direct downshifts by activating an additional choosing sleeve.
Another embodiment of the selector device according to the invention that is once again advantageous for multi-speed transmissions and allows direct gear changes that involve skipping two or three or more gears by activating an additional choosing sleeve, this being achieved in this case for the upshifts.
The invention can be employed with particular advantage in a 5- or 6-speed transmission, in which it is possible to skip two or three gears in the case of direct upshifts by activating an additional choosing sleeve.
While the previous embodiments of the selector device according to the invention envisage the use of at least two choosing sleeves with associated auxiliary mechanisms and brakes, the number of gear-change options involving skipping gears is increased in a further advantageous embodiment of the selector device according to the invention by the use of least three choosing sleeves. In this embodiment, two choosing sleeves are provided in all cases and their auxiliary mechanisms each define the minimum differential angle of rotation, which includes just two adjacent significant angular positions, one auxiliary mechanism being designed with an upshift characteristic and the other with a downshift characteristic in terms of the respective direction of action. In this embodiment, a third choosing sleeve is used, the auxiliary mechanism of whichxe2x80x94which is designed with an upshift or downshift characteristicxe2x80x94defines a larger differential angle of rotation, which is at least twice as great as the minimum differential angle of rotation.
In another advantageous embodiment of the selector device according to the invention, the number of gear-change options involving skipping gears is increased by the use of at least three choosing sleeves. In this embodiment, just one choosing sleeve is provided, by way of the auxiliary mechanism of which, which is designed with an upshift characteristic, only the minimum differential angle of rotation is defined. The respective differential angle of rotation of the two other auxiliary mechanisms is at least twice as great, one auxiliary mechanism being designed with an upshift characteristic and the other with a downshift characteristic.
Finally, in another embodiment of the selector device according to the invention, it is advantageous that the number of gear-change options involving skipping gears can be further increased by the use of at least four choosing sleeves with associated auxiliary mechanisms and brakes. In this embodiment, two auxiliary mechanisms, each associated with one choosing sleeve, are provided in all cases. These auxiliary mechanisms define only the minimum differential angle of rotation, and one of them has an upshift characteristic and the other has a downshift characteristic. In this embodiment, use is also made, in all cases, of two auxiliary transmissions, which are each associated with one choosing sleeve and define equal or unequal differential angles of rotation of greater magnitude. One of them has an upshift character, and the other has a downshift character.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.